Drill: Calculate the volume of gas released

at 227oC under 83.1 kPa pressure when 320 kg of

NH4NO3 is exploded forming N2, O2, & H2O:

Thermo-chemistry

AP Chm

Chapter 8

Chm II

Chapter 15

Thermochemistry

•The study of heat transfer in

chemical reactions

Thermochemistry Topics

•Heat change

•Calorimetry

•Thermo-Chm-Eq

Thermo-chemical

Terms

Heat (H)•A form of energy

that can flow between samples of

matter

Heat cannot be measured directly; thus, we measure heat change (H)

Enthalpy•Another name for

heat

H

Enthalpy Change•Heat that can flow

in/out of a system

H

System•That part of nature upon which attention

is focused

Surroundings•That part of nature

around the part upon which we are

focused

Reaction Coordinate

•A graph of energy change versus time in a chemical reaction

Time

Ene

rgy

RP

Exothermic Rxn•Chemical reactions

that release, give off heat, or lose

heat

Exothermic Rxn•Products will

contain less heat than the reactants

H < 0

Endothermic Rxn

•Chemical reactions that absorb, take in heat, or gain heat

Endothermic Rxn•Products will

contain more heat than the reactants

H > 0

Topic: Heat

Change

Specific Heat•The heat required to raise one gram of a substance 1oC

•C: (J/goC, J/kgoK)

Specific Heat Formula

H = mCT

Heat of Fusion•The heat required to melt one gram of a substance at its normal MP

•Hf: (J/g or J/kg)

Heat of Fusion Formula

H = mHf

Heat of Vaporization

•The heat required to boil one gram of a substance at its normal BP

•Hv: (J/g or J/kg)

Heat of Vap. Formula

H = mHv

AP CHM HW•Read: Chapter 8•Work problems:

5 & 17•Page: 234

CHM II HW•Read: Chapter 9•Work problems:

•Page:

Calculate the heat change when 10.0 g H2O goes from –100.0oC to 200oC.MP = 0oC BP = 100oCHf = 334 J/g HV = 2260 J/g

Cice = 2.06 J/gKCwater = 4.18 J/gK Csteam = 2.02 J/gK

Drill: Calculate the heat required to change 25 g

of water from 140.0oC to 60.0oC

MP = 0oC BP = 100oCHf = 334 J/g HV = 2260 J/g

Cice = 2.06 J/gKCwater = 4.18 J/gK Csteam = 2.02 J/gK

Topic: Calorimetry

Calorimetry•A method to measure the

experimental heat transfer in a system

Calorimeter•Device used to measure heat transfer

•A calorimeter is an adiabatic system

•Experimental yield

Adiabatic System•A system that exchanges zero heat with its surroundings

Hsystem = 0

H (J or kJ)H = q = the heat or enthalpy change in a system

Hsys = mcTsys parts

CalorimetryHsystem = 0

Hsys = Hcal + Hrxn

Hrxn = -Hcal

Hrxn = -mcTcal

When Q reacts in a 1.5 kg calorimeter containing 2.5 kg water the temp changes from

22.5oC to 26.5oC.Calculate Hrxn. Cwater = 4.18 J/gK Ccal = 2.00 J/gK

Chm II HW

Problems: 64 & 65

Page: 641-641

AP Chm HW

Problems: 8 & 9

Page: 234

When X reacts in a 2.0 kg calorimeter containing 1.5 kg water, the temp changes

from 22.5oC to 30.5oC. Calculate Hrxn. Cwater = 4.18 J/gK Ccal = 1.50 J/gK

When Z reacts in a 1.0 kg calorimeter containing 2.0 kg water, T = 22.5oC to 32.5oC. Calculate Hrxn.

Cwater = 4.18 J/gK Ccal = 2.00 J/gK

Drill: When 40.0 g NH4NO3 dissolves in

460.0 g water at 25.0oC, the temp. falls to 22.5.oC.

Calculate the Hosoln for

NH4NO3. Csoln = 4.00 J/gK

Topic: Thermochemical

Equation (TCE)

Thermo-chemical Equation

Terms

Heat of Reaction•The heat or enthalpy change of a chemical reaction

Hrxn

Typical Reaction

•HCl + NaOH NaCl + HOH

Heat of Solution

•The heat or enthalpy change when a substance is dissolved

Hsoln

Typical Ionization

KCl

K+(aq) + Cl-

(aq)

Heat of Combustion•The heat or enthalpy change when a substance is burned

Hcombustion

Combustion Reaction

•CxHy + O2

CO2 + HOH

Heat of Formation•The heat required to form one mole of a compound from pure elements

Hfo (kJ/mole)

Rxn Making Cpds from ele

H2 + ½ O2 H2O

The Degree Symbol•Indicates standard conditions & molar

quantities by itself or from a balanced

equation.

AP Chm HW•Problem: 41

On page 236

Chm II HW•Problem: 37

On page 638

Gibb’s Free Energy•Energy of a system that can be converted to work

•Determines spontaneity

G

Energy of Formation•The energy required to form one mole of a compound from pure elements

Gfo (kJ/mole)

Exergonic Reaction•A reaction in which free energy is given off

G < 0

Endergonic Reaction

•A reaction in which free energy is absorbed

G > 0

Exergonic Reaction•A reaction which can be spontaneous

G < 0

Endergonic Reaction

•A reaction which cannot be spontaneous

G > 0

Reaction at Equilibrium

G = 0

Interrelation Term (G)

G interrelates thermochemistry,

chemical equilibria,

& electrochemistry

Entropy•A measure of disorder

So

Entropy of Formation•The entropy of one mole of a substance

•Sfo (J/moleoK)

•Sfo (kJ/moleoK)

Drill: Define:• Heat of reaction

• Heat of solution

• Heat of formation

• Energy of formation

• Entropy of formation

Drill: Identify type of rxn when:

G > 0G < 0G = 0

Thermochemical Equation

•An equation that shows changes in heat, energy, etc

Thermochemical Equation

Ho

rxn Hf

o

productsHf

o

reactants

Thermochemical Equation

Go

rxn Gf

o

productsGf

o

reactants

Thermochemical Equation

So

rxnSf

o

products

Sfo

reactants

Thermochemical Equation

•Stoichiometry of heat change

•Solves theoretical yield

Interrelating Equation

GH

S

Drill: Define:•Heat of Rxn

•Heat of Solution

•Heat of Combustion

•Heat of Formation

In stoichoimetric calculations, the TCE

is used for molar conversions from

mole to heat or heat to moles

Calculate H, G, & S when 13.6 g of CaSO4 is changed

into CaO + SO2 + O2 at 25oC

Cmpd CaSO4 SO2 CaO

Hf

o -1434.1 -296.8 -635.1

Gf

o -1321.8 -300.2 -604.0

AP Homework•Problem: 41b

On page 236

Chm II HW•Problem: 36

On page 638

Calculate H, G, & S when 19.7 kg of BaCO3 is decomposed into BaO + CO2

Cmpd BaCO3 CO2 . BaO

Hf

o -1216.3 -393.5 -553.5

Gf

o -1137.6 -394.4 -525.1

Sf

o 112.1 213.6 70.4

Drill: Calculate Ho

rxn for:A + B2C3 AC2 + B

Compd B2C3 AC2

Hfo(kJ/mole) -150 -250

Gfo(kJ/mole) -175 -225

Calculate the potential H, G, & S for the reaction & Sf

o for

O2 when burning 8.8 kg of C3H8 Cpd C3H8 CO2 H2O

Hf

o-103.8 -393.5 -241.8

Gf

o- 23.5 -394.4 -228.6

Sf

o269.9 213.6 188.7

AP CHM HW•Work problem 45 on page 236

Lab Results: Cup H2O NaOH Thermo

5.0 g 50.0 g 4.0 g 15.0 g Ti = 22.0

oC Tf = 27.0

oC

Cmpd NaOH Na+ OH-

Hf

o -425.6 -240.1 -230.0

Determine: theoretical and experimental heat changes

Drill: Calculate Ho, Go, & So when P + QR PR2 + QCompd QR PR2

Hfo(kJ/mole) -250 -450

Gfo(kJ/mole) -225 -425

Chm II HW•Problem: 63

•Page: 640

Review Quiz

Heat Change•Calculate the heat change when the temperature of 1.0 kg H2O is changed from –100.0oC to 200.0oC.

When 2.00 g NaOH dissolves in a 1.0 L water in a 2.5 kg calorimeter, the temp. went

from 22.5oC to 26.5oC. Calculate: Ho

soln Cwater = 4.18 J/gK Ccal = 2.00 J/gK

Bond Energy•The energy change

when one mole of bonds are broken

Ho

bond

Bond Equation

Hbondo

rxnHbond

o

products

Hbondo

reactants)

Bond Energies (kJ/mole)

C-C 347 O=O

C-H 414 498

O-H 464

C=O 715

Calculate the heat change when 1.00

mole of C2H6 is burned.

Drill:Calculate H, G, & S in the production of 831mL

ammonia at 227oC under

250.0 kPa pressureCompd NH3

Hfo -46.1

Gfo -16.5

1st Law Thermodynamics

•Total energy change = heat + work

E = q + W

Work•W = Fd

•P = F/A

•V = Ad

•W = PV = nRT

2nd Law Thermodynamics

•Total entropy in a system always increases assuming no energy is added to the system

Thermodynamic Rxns are State

Rxns

State Reaction•Reactions that are independent of the

path; thus not dependent on intermediates

Lab 8:•Thermochemistry•HW: P 49•Page: 236

Drill: Calculate Ho, Go, So, & solve Teq when:

A + BC AC2 + BCompd BC AC2

Hfo(kJ/mole) -150 -250

Gfo(kJ/mole) -125 -225

Hess’s LawHrxn is the same

whether it occurs in a single step or a series

of steps.

Calculate Ho & Go, & S & Teq at -23oC when:

A + BC AC + BCompd BC ACHf

o(kJ/mole) -150 -250Gf

o(kJ/mole) -175 -225

Write TE for the process2 A + B C + D

C + A H

D + B 2 K

H + K M + B

K + M Product

Write TE for the process2 A + B C + D

C + A H

D + B 2 K

H + K M + B

K + M Product

AP Homework•Problem: 32 & 33

On page 235

Write TE for the process2 A + 2 B C + D

C + A 2 H

D + B 2 K

H + K P + B

Write TE for the process2 A + 2 B C + D

C + A 2 H

D + B 2 K

2 H + 2 K 2 P + 2 B

Drill: Calculate Horxn for

the production of CaCO3 from CaO & CO2

Hf

o

(kJ/mole)

CaCO3 CaO CO2

-1206.9 -635.1 -393.5

When 25.0 g CaCO3 is made

from CaO & CO2 in a 500. g calorimeter (C = 1.50 J/gK) containing 250 g of water

(C = 4.18 J/gK), the water changes from 25.0oC to 45.0oC. Calculate Hrxn/mole of CaCO3

Calculate the % yield from the

results of the last two slides

Bond Equation

Hbondo

rxnHbond

o

products

Hbondo

reactants)

Bond Energies (kJ/mole)

C-C 347 O=O

C-H 414 685

O-H 464

C=O 715

Calculate the heat change when 6.0

kg of ethane (C2H6) is burned

in excess oxygen.

Substance Hof(kJ/mole)

S Hof S Ho

f

A -100 H -150B -150 K -200C -50 P -250D -125 Q -300

Solve Horxn for TE

A + B 2 C + 2 D

C + A 2 H + P

D + B 2 K + P

H + K P + Q

Solve Horxn for TE

A + B 2 C + 2 D

2C + 2A 4 H + 2P

2D + 2B 4K + 2P

4H + 4K 4P + 4Q

Test on Thermochemistry

on Tuesday

Review

What does each symbol represent?

Define what is represents:

H:G:S:

Calculate Htotal, when 40.0 g of

H2O is changed from - 25oC to

125oC. FPw = 0.0oC

BPw = 100.0 oC Hv = 2260 J/gCice = 2.06 (J/g K) Hf = 334 J/gCwater = 4.18 (J/g K)Csteam = 2.02 (J/g K)

Calculate Ho, Go, & So for N2O5 + H2O HNO3

Cpd N2O5 H2O HNO3 Hf

o -11.3 -285.8 -174.1

Gfo -10.4 -237.2 -151.5

Solve Ho for TE X + Y 2 W + 2 Z 60 kJ

W + X 2 R + P 40 kJ

2 S + P Z + Y 50 kJ

R + S P + Q 80 kJ

Ho for TE X + Y 2 W + 2 Z 60 kJ

2W + 2X 4 R + 2P 80 kJ

2Z + 2Y 4 S + 2P -100 kJ

4 R + 4S 4P + 4Q 320 kJ

3X + 3Y 8P + 4Q 360 kJ

Calculate Ho, G

o, & S for

AD2 + BC AC2 + BD

at (-23oC)

Cpd BC AD2 AC2 BD

Hf

o -150 -250 -300 -175

Gf

o -125 -225 -250 -150

Sf

o 75 50 80 ?

Determine Sf

o

BD

Calculate Ho, Go, & So for PbO2 + CO CO2 + Pb

Cpd PbO2 CO CO2 Hf

o -277.4 -110.5 -393.5

Gfo -217.4 -137.2 -394.4

Calculate: Teq & H of 48 g PbO2

Test Tomorrow

When 4.20 g MgCO3 is decomposed to MgO & CO2 in a 2500.0 g calorimeter (C = 2.00 J/gK) containing 1.0.kg of water (C = 4.18 J/gK), the water changes from 23.00oC to 13.00oC. Calculate the heat of rxn/mole of MgCO3

AP Homework:Read: Chapter 9Power Point: 17

Chm II Homework:Read: Chapter 16Power Point: 19